1. Field of the Invention
The present invention relates to a method and an apparatus for inspecting a lens-fitted photo film unit. More particularly, the present invention relates to a method and an apparatus for inspecting a lens-fitted photo film unit incorporating an electronic flash device.
2. Description Related to the Prior Art
There is a lens-fitted photo film unit pre-loaded with photo film and incorporating a simple structure for taking exposures. In the lens-fitted photo film unit, the photo film is wound each time after one frame is exposed. The movement of the photo film in the winding operation is utilized for cocking a shutter mechanism, a one-frame advancement of the photo film and a rotation of a counter wheel by one step. The lens-fitted photo film unit incorporates an electronic flash device which emanates flash light in response to a releasing operation of the shutter mechanism, so that a photograph can be taken easily even indoors or at night.
The prevalent types of the lens-fitted photo film unit are pre-loaded with a photo film cassette of the 135 type. Also there is a type of lens-fitted photo film unit pre-loaded with the photo film cassette of the IX240 type. In the photo film cassette of the IX240 type, the photo film has a train of perforations arranged therein. The photo film cassette includes a plastic cassette shell for containing a roll of the photo film.
The photo film includes an effective exposure region and ineffective regions defined different from the effective exposure region. The effective exposure region is adapted to taking exposures in the lens-fitted photo film unit or a camera. The ineffective regions are determined as areas where exposures are inhibited. The perforations are arranged along an edge only of the effective exposure region of the photo film. The perforations are alternately arranged with two intervals being longer and shorter which are alternately repeated. One frame is exposed inside each of sections having the longer interval. Sections having the shorter interval are associated with intervals between the adjacent frames. The photo film for the photo film cassette does not have extra frames, but has the number of available frames determined for the photo film. The ineffective regions are used for development, and wound back into the cassette shell.
In a manufacturing process of the lens-fitted photo film unit, performance of the shutter mechanism is inspected after loading of the photo film together with inspection of winding the photo film. For example, a shutter speed of the shutter mechanism is measured and evaluated for the inspection of the shutter mechanism.
For the lens-fitted photo film unit with the flash device, it is conventionally general to inspect the shutter mechanism in a manner separate from inspection of the flash device. This is because a photo sensor of a reflection type for detecting movement of a shutter blade should be prevented from being affected by flash light of the flash device, and also because the ineffective region should be kept from being exposed by the flash light. However the inspecting manner of the shutter mechanism separate from the inspection of the flash device takes long time, is conspicuously slow in the manufacturing process, and is inconsistent to improvement of efficiency.